Driver circuit structure

ABSTRACT

Disclosed is a driver circuit structure integrated in a display panel. The driver circuit structure includes a plurality of transistors and a backup transistor. After completing the driver circuit structure, the disclosure inspects it to find an inactive transistor. The inspection process first, isolates the electrical connection between the inactive transistor and the first electrode line and/or the electrical connection between the inactive transistor and the second electrode line. Next, the source electrode of the backup transistor and the first electrode line and/or electrically connecting the drain electrode of the backup transistor and the second electrode line are electrical connected.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No.098119886, filed on Jun. 15, 2009, the entirety of which is incorporatedby reference herein.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to a gate driver on array (GOA) structureintegrated in a display panel, and in particular relates to a repairableGOA structure and a display panel utilizing the same.

2. Description of the Related Art

Liquid crystal displays (LCD) are widely applied in electronic displayproducts such as televisions, laptop computers, mobile phones, personaldigital assistants (PDA), and the likes. An LCD includes a data driver,scan driver, and liquid crystal display panel, wherein the liquidcrystal display panel has a pixel array, and the corresponding pixelrows of the pixel array are sequentially switched on by the scan driver,such that the data driver may transfer the pixel data to the pixels todisplay images.

Gate drivers and source drivers are mostly adopted in numerous paneldesigns to produce gate pulse signals and data signals. Because thepolycrystalline silicon made of the low temperature polycrystallinesilicon (LTPS) process has higher mobility and high practicability, theLTPS process is widely applied to manufacturing circuits on glass. Theamorphous silicon has lower mobility, however, its cost is lower.Recently, application of the amorphous silicon process is used to formcircuits on the glass, such as gate driver shift registers (so-calledintegrated driver circuits).

A gate driver on array (GOA) product has shift register circuits on aglass substrate. The products however, during an array process, easilydeteriorate due to low process stability. For example, some transistorsof the shift registers would not be able to normally work due to processparticles thereon. In such a case, the shift transistors including onlyone inactive transistor would not operate. Therefore, cost and yield ofthe GOA products are dramatically influenced.

BRIEF SUMMARY OF THE DISCLOSURE

The disclosure provides a driver circuit structure integrated in adisplay panel, and the driver circuit structure comprising: a pluralityof transistors, wherein each of the transistors has a source electrodeelectrically connected to a first electrode line, and a drain electrodeelectrically connected to a second electrode line, respectively; and abackup transistor, wherein the backup transistor has a source electrodenot electrically connected to the first electrode line, and/or a drainelectrode not electrically connected to the second electrode line.

The disclosure further provides a method for repairing a driver circuitstructure, comprising: inspecting the driver circuit structure to findan inactive transistor; electrically isolating the connection betweenthe inactive transistor and the first electrode line and/or theconnection between the inactive transistor and the second electrodeline; and electrically connecting a backup transistor source electrodeand the first electrode line and/or electrically connecting a backuptransistor drain electrode and the second electrode line, wherein thenumber of the electrically isolated inactive transistors is similar tothe number of the electrically connected backup transistors.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a diagram showing a display panel in one embodiment of thedisclosure;

FIG. 2 is a circuit diagram of a driver circuit structure in oneembodiment of the disclosure;

FIGS. 3A-3B are top views of a driver circuit structure in oneembodiment of the disclosure;

FIG. 4 is a cross sectional view of a cross section line a-b in a drivercircuit structure in one embodiment of the disclosure;

FIG. 5 is a cross sectional view of a cross section line c-d in a drivercircuit structure before a repair process in one embodiment of thedisclosure;

FIG. 6 is a cross sectional view of a cross section line c-d in a drivercircuit structure after a repair process in one embodiment of thedisclosure;

FIGS. 7A-7B are top views of a driver circuit structure in oneembodiment of the disclosure; and

FIGS. 8A-8B are top views of a driver circuit structure in oneembodiment of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

The following description is of the best-contemplated mode of carryingout the disclosure. This description is made for the purpose ofillustrating the general principles of the disclosure and should not betaken in a limiting sense. The scope of the disclosure is bestdetermined by reference to the appended claims.

As shown in FIG. 1, the display panel 100 has a display region 102 and aperipheral line region 104 surrounding the display region 102. Thedisplay region 102 has a plurality of pixels 110, and the peripheralline region 102 has a gate driver on array structure. The gate driver onarray structure has high ratio of channel width to channel length,thereby improving the response rate and the resolution of the displaypanel 100. However, it is difficult to repair the electrode of the gatedriver on array structure when it is polluted, such that the displayeffect of the pixels 110 will be influenced. As such, the disclosureprovides a design about the gate driver on array structure (shiftregister), wherein the gate driver on array structure is composed of aplurality of thin film transistors electrically connected in parallel.Even if part of the conductive pattern is short due to processparticles, it can still be repaired to enhance the display panel 100yield and further improve the visual quality.

FIG. 2 shows a circuit diagram of a driver circuit structure, integratedin a display panel, serving as a gate driver on array structure or ashift register in the display panel. The driver circuit structureincludes a plurality of transistors 11B, wherein each of the transistors11B has a source electrode electrically connected to a first electrodeline 17A, and each of the transistors 11B has a drain electrodeelectrically connected to a second electrode line 17B. The drivercircuit structure further includes a backup transistor 11A, and thesource electrode of the backup transistor is not electrically connectedto the first electrode line 17A. If some transistor 11B is polluted bythe particle and being inactive, the connection between the sourceelectrode of the polluted transistor 11B and the first electrode line17A can be electrically isolated, and the source electrode of the backuptransistor 11A can be electrically connected to the first electrode line17A. The number of transistors after repair is not changed. For example,the driver circuit structure has eight transistors 11B and four backuptransistors 11A, and two transistors are polluted by process particles.Thereafter, the electrical connection between the source electrode ofthe two polluted transistors 11B and the first electrode line 17A isisolated, and the source electrode of the two backup transistors 11A iselectrically connected to the first electrode line 17A. Accordingly, therepaired driver circuit structure still has eight normal transistors.

In one embodiment, the backup transistor 11A is located on the terminalof the driver circuit structure. In another embodiment, the backuptransistor 11A is inserted between the transistors 11B.

The described repair process may not only isolate the electricalconnection between the source electrode of the polluted transistor 11Band the first electrode line 17A, but also further isolate theconnection between the drain electrode of the polluted transistor 11Band the second electrode line 17B.

As shown in FIG. 2, the source electrode of the backup transistor 11A isnot electrically connected to the first electrode line 17A before therepair process. In another embodiment, the drain electrode of the backuptransistor 11A is not electrically connected to the second electrodeline 17B before the repair process. In a further embodiment, both of thesource electrode and the drain electrode of the backup transistor 11Aare not electrically connected to the first electrode line 17A and thesecond electrode line 17B before the repair process. Thus, it isimportant that the backup transistor 11A is not effective before therepair process. The source and drain electrodes of the backup transistor11A will electrically connect to the first electrode line 17A and thesecond electrode line 17B, respectively, thereby replacing theelectrically isolated transistor 11B.

FIG. 3A shows the top view of the described driver circuit structure,FIG. 4 shows the sectional view of line a-b in FIG. 3A, and FIG. 5 showsthe sectional view of line c-d in FIG. 3A. Note that the driver circuitstructure in FIG. 3A is only for illustration and does not limit thedisclosure. For example, a gate electrode layer, a semiconductor layer,and a source/drain electrode layer are sequentially formed on thesubstrate of the driver circuit structure in FIG. 3A. In otherembodiments, however, a source/drain electrode, a semiconductor layer,and a gate electrode layer are sequentially formed on a substrate.

The method for manufacturing the driver circuit structure in FIG. 3A isdescribed below. Please also reference FIGS. 4 and 5 for clarity. First,a substrate 10 is provided. The substrate 10 can be transparent materialsuch as glass, quartz, or other suitable transparent materials; opaquematerial such as ceramic, wafer, or other suitable opaque materials; orflexible material such as plastic, rubber, polyester, polycarbonate, orother suitable flexible materials. Subsequently, a first conductivelayer (not shown) is formed on the substrate. The first conductive layerincludes metal such as Ti, Ta, Ag, Au, Pt, Cu, Al, Mo, Nd, W, Cr, Rh,Re, Ru, Co, other suitable metals, or alloys thereof; and metal oxidesuch as indium tin oxide (ITO), indium zinc oxide (IZO), ormulti-layered structures thereof. A lithography process is performed onthe first conductive layer and following an etching step is performed todefine a gate electrode layer 13A and a contact pad 13B. As shown inFIG. 3A, the gate electrode 13A and the contact pad 13B are separated bya distance, and they are not electrically connected.

Next, a first insulation layer 14 is formed on the gate electrode layer13A and the contact pad 13B, and a semiconductor layer 15 is formedoverlying the first insulation layer 14 on the gate electrode layer 13A.The first insulation layer 14 can be organic material such asphotoresist, organic silicon compound, or other suitable organicmaterials; inorganic material such as silicon nitride, silicon oxide,silicon oxynitride, silicon oxycarbide, silicon carbide, or othersuitable inorganic materials; or combinations thereof. The semiconductorlayer 15 includes typical semiconductor material such as amorphoussilicon, polycrystalline silicon, microcrystalline silicon, singlecrystalline silicon, or combinations thereof. The formation of thesemiconductor layer 15 can be by chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), rapid thermalchemical vapor deposition (RTCVD), ultra-high vacuum chemical vapordeposition (UHV/CVD), or molecular beam epitaxy (MBE).

Next, a second conductive layer (not shown) is formed on thesemiconductor layer 15 and the first insulation layer 14. The secondmetal layer includes metal such as Ti, Ta, Ag, Au, Pt, Cu, Al, Mo, Nd,W, Cr, Rh, Re, Ru, Co, other suitable metals, alloys thereof, ormulti-layered structures thereof. A lithography process is performed onthe second conductive layer and following and etching step is performedto define the first electrode line 17A, the source electrodes 21 of thetransistors 11B and the backup transistor 11A, the second electrode line17B, the drain electrode 19A of the backup transistor 11A, and the drainelectrodes 19B of the transistors 11B. As shown in FIG. 2, the firstelectrode line 17A electrically connects to the source electrodes 21 ofthe transistors 11B and the backup transistor 11A, and the secondelectrode line 17B only electrically connects to the drain electrode 19Bof the transistor 11B. As shown in FIG. 3A, the backup transistor 11A islocated at the outer side of the transistors 11B, and the contact pad13B is located at the terminal of the second electrode line 17B. Thesecond electrode line 17B overlaps part of the contact pad 13B, anddrain electrode 19A of the backup transistor 11A extends to define anextending part on the contact pad 13B. The extending part of the drainelectrode 19A of the backup transistor 11A on the contact pad 13B has awidth W₃ greater than the width W₄ of the drain electrode 19A of thebackup transistor 11A, and the extending part of the drain electrode 19Aof the backup transistor 11A, on the contact pad 13B has a length Lsimilar to the width W₂ of the contact pad 13B and the width W₁ of thesecond electrode line 17B. Therefore, a subsequent laser welding processmay electrically connect the contact pad 13B and the second electrodeline 17B without misalignment risk, and electrically connect the contactpad 13B and the drain electrode 19A of the backup transistor 11A on thecontact pad 13B without misalignment risk.

Finally, a second insulation layer 23 is formed to cover the describedstructure. Material selection and the formation method of the secondinsulation layer 23 are similar to that of the first insulation layer14, and the insulation layers 14 and 23 may adopt same or differentmaterials. The description of a driver circuit structure in oneembodiment of the disclosure is completed.

After completing the described driver circuit structure, the transistors11B are inspected by image matching and the likes to check them beingclean or polluted. If some transistor 11B is polluted, the electricalconnection

between the drain electrode 19B of the polluted transistor 11B and thesecond electrode line 17B is isolated by laser ablation, the contact pad13B and the second electrode line 17B are electrically connected intheir overlap region ⊕ by laser welding and the likes, and the contactpad 13B and the backup transistor drain electrode 19A are electricallyconnected in their overlap region ⊕ by laser welding and the likes.FIGS. 5 and 6 show the structure before and after the laser welding,respectively. The laser is applied to burn through the first insulationlayer 14 between the drain electrode 19A of the backup transistor 11Aand the contact pad 13B and the first insulation layer 14 between theterminal of the second electrode line 17B and the contact pad 13B.Simultaneously, the laser also melts part of the drain electrode 19A ofthe backup transistor 11A and terminal part of the second electrode line17B to electrically connect the contact pad 13B.

In another embodiment, the first electrode line 17A may be disposedbesides the gate electrode layer 13A and the semiconductor layer 15 asshown in FIG. 3B. As such, the source electrode 21 of the backuptransistor 11A can be electrically isolated from the first electrodeline 17A. The first electrode line 17A may adopt the design of thesecond electrode line 17B and the corresponding contact pad 13B. Thefirst electrode line 17A overlaps part of another contact pad 13C. Thesource electrode 21 of the backup transistor 11A extends to define anextending part on another contact pad 13C. In this embodiment, thebackup transistor 11A is located at the outside of the transistors 11B,and another contact pad 13C is located at the terminal of the firstelectrode line 17A. The extending part of the backup transistor sourceelectrode 21 on another contact pad 13C has a width W3′ greater than thewidth W4′ of the backup transistor source electrode 21A, and theextending part of the backup transistor source electrode 21A on anothercontact pad 13C has a length L′ similar to the width of another contactpad and the width W1′ of the first electrode line 17A. Therefore, asubsequent laser welding process may electrically connect anothercontact pad 13C and the first electrode line 17A without misalignmentrisk, and electrically connect another contact pad 13C and the extendingpart of the backup transistor source electrode 21A on another contactpad 13C without misalignment risk. After completing the described drivercircuit structure, the transistors 11B are inspected by image matchingand the likes to check if they are polluted. If some transistors 11B arepolluted, the electrical connection

between the source electrode 21B of the polluted transistor 11B and thefirst electrode line 17A is isolated by laser ablation, another contactpad 13C and the first electrode line 17A are electrically connected intheir overlap region by laser welding and the likes, and another contactpad 13C and the backup transistor source electrode 21A are electricallyconnected in their overlap region by laser welding and the likes.Similar to the structure before and after the laser welding in FIGS. 5and 6, the laser is applied to burn through the first insulation layer14 between the source electrode 21 of the backup transistor 11A andanother contact pad 13C and the first insulation layer 14 between theterminal of the first electrode line 17A and another contact pad 13C.Simultaneously, the laser also melts part of the source electrode 21A ofthe backup transistor 11A and terminal part of the first electrode line17A to electrically connect another contact pad 13C. It is understoodthat if another contact pad 13C is adopted with the backup transistorsource electrode 21A electrically isolated from the first electrode line17A, the contact pad 13B can be omitted and the second electrode line17B may electrically connect the drain electrode 19A of the backuptransistor 11A.

In FIG. 3A, the driver circuit structure only includes one backuptransistor 11A. In another embodiment, it includes a plurality of thebackup transistors 11A as shown in FIG. 7A. If more than one of thetransistors 11B are polluted by the particles, they are replaced withmore than one of the backup transistors 11A provided by the drivercircuit structure in FIG. 7A. After image matching, the electricalconnection

between the drain electrode 19B of the polluted transistor 11B and thesecond electrode line 17B is isolated by laser ablation, the contact pad13B and the second electrode line 17B are electrically connected intheir overlap region ⊕ by laser welding and the likes, and the contactpad 13B and the drain electrode 19A of the backup transistor 11A areelectrically connected in their overlap region ⊕ by laser welding andthe likes. It is understood that the number of the electricallyconnected backup transistors is similar to the number of the inactivetransistors. For example in FIG. 7A, if the inactive transistor 11B isonly one, it will only need to electrically connect the right-sided orleft-sided backup transistor 11A other than both backup transistors 11A.Similarly, the first electrode line 17A may be disposed besides the gateelectrode layer 13A and the semiconductor layer 15 as shown in FIG. 7B.As such, the source electrode 21A of the backup transistor 11A can beelectrically isolated from the first electrode line 17A. The firstelectrode line 17A may adopt the design of another contact pad 13C asdescribed above. The design and relative repair process of the othercontact pad 13C is similar to the previous description.

The backup transistors 11A in FIG. 6 are located in the outside of thetransistors 11B. In another embodiment, the backup transistor may bedisposed between the transistors as shown in FIG. 8A, wherein theelectrode line has a meander line structure to collocate the contactpad. As shown in FIG. 8A, the backup transistor 11A is located betweenthe transistors 11B, and the second electrode line 17B has a meanderline structure in the overlap region of the contact pad 13B and thesecond electrode line 17B, wherein the meander line structure has aconvex part protruding from the second electrode line 17B and a concavepart overlapping the contact pad 13B. The extending part of the backuptransistor drain electrode 19A on the contact pad 13B has a width W₃greater than the width W₄ of the backup transistor drain electrode 19A,and the extending part of the backup transistor drain electrode 19A onthe contact pad 13B has a length L less than the width W₁ of the secondelectrode line 17B. Therefore, a subsequent laser welding process mayelectrically connect the contact pad 13B and the second electrode line17B without misalignment risk, and electrically connect the contact pad13B and the extending part of the backup transistor drain electrode 19Aon the contact pad 13B without misalignment risk.

After completing the described driver circuit structure, the transistors11B are inspected by image matching and the likes to check if they arepolluted. If some transistors 11B are polluted, the electricalconnection

between the drain electrode 19B of the polluted transistor 11B and thesecond electrode line 17B is isolated by laser ablation, the contact pad13 and the concave part of the meander line structure of the secondelectrode line 17B are electrically connected in their overlap region(not symbolized) by laser welding and the likes, and the contact pad 13Band the backup transistor drain electrode 19A are electrically connectedin their overlap region ⊕ by laser welding and the likes. The laserwelding process applied to electrically connect the backup transistordrain electrode 19A, the second electrode line 17B, and the contact pad13B is shown in FIG. 5 and, in FIG. 6, the cross sectional views of thec-d line before and after the laser welding is shown. The firstinsulation layer 14 between the contact pad 13B and the drain electrode19A of the backup transistor 11A and between the contact pad 13B and theconcave part of the meander line structure of the second electrode line17B is burnt through by laser. Simultaneously, part of the drainelectrode 19A of the backup transistor 11A and concave part of themeander line structure of the second electrode line 17B are melt toelectrically connect the contact pad 13B.

The described meander line structure is benefit to form severalindividual backup transistors 11A. Even if some backup transistors arepolluted, the other clean backup transistors 11A, the second electrodeline 17B, and the contact pad 13B can still be electrically connected.As such, it is not necessary to electrically connect the polluted backuptransistors 11A, and then electrically isolate the electrical connection

between the extending part of the source electrode 19A on the contactpad 13 and the drain electrode 19A, as shown in FIG. 7A. Similarly, thefirst electrode line 17A in FIG. 8A may locate besides the gateelectrode layer 13A and the semiconductor layer 15, and further has themeander line structure of the second electrode line 17B. Accordingly,the backup transistor 11A located between the transistors 11B may notelectrically connect to the first electrode line 17A, and may adoptdesigns of another contact pad 13C as shown in FIG. 8B. The design andrelative repair process of the first electrode line 17A having themeander line structure and a corresponding contact pad 13C is similar tothe previous descriptions.

In a further embodiment, the meander line structure in FIGS. 8A-8B canbe collocated with the designs in FIGS. 3A-3B or FIGS. 7A-7B. Thedescribed technique allows the number of transistors after repair toremain the same as that before repair, thereby efficiently enhancingproduct yield.

While the disclosure has been described by way of example and in termsof the preferred embodiments, it is to be understood that the disclosureis not limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

What is claimed is:
 1. A driver circuit structure integrated in adisplay panel, and the driver circuit structure comprising: a pluralityof transistors, wherein each of the transistors has a source electrodeelectrically connected to a first electrode line, and a drain electrodeelectrically connected to a second electrode line, respectively; abackup transistor, wherein the backup transistor has a source electrodenot electrically connected to the first electrode line, and/or a drainelectrode not electrically connected to the second electrode line; agate electrode layer and a contact pad on a substrate; a firstinsulation layer on the gate electrode layer and the contact pad; and asemiconductor layer overlying the first insulation layer on the gateelectrode layer, wherein: the source/drain electrodes of the transistorsare on the semiconductor layer, and the source/drain electrodes of thetransistors are electrically connected to the first/second electrodelines, respectively; the first electrode line and/or the secondelectrode line overlap part of the contact pad; and the backuptransistor has a source electrode and/or a drain electrode extending todefine an extending part on the contact pad.
 2. The driver circuitstructure as claimed in claim 1, wherein the backup transistor islocated at the outer side of the transistors, and the contact pad islocated at the terminal of the first electrode line and/or the secondelectrode line.
 3. The driver circuit structure as claimed in claim 2,wherein the width of the extending part of the source electrode and/orthe drain electrode of the backup transistor is greater than the widthof the source electrode and/or the drain electrode of the backuptransistor, and wherein the length of the extending part of the sourceelectrode and/or the drain electrode of the backup transistor, the widthof the contact pad, and the width of the first electrode line and/or thesecond electrode line are same.
 4. The driver circuit structure asclaimed in claim 1, wherein the backup transistor is located between thetransistors, and the first electrode line and/or the second electrodeline has a meander line structure in the overlap region of the contactpad and the first electrode line and/or the second electrode line, andthe meander line structure has a convex part protruding from the firstelectrode line and/or the second electrode line and a concave partoverlapping the contact pad.
 5. The driver circuit structure as claimedin claim 4, wherein the width of the extending part of the sourceelectrode and/or the drain electrode of the backup transistor is greaterthan the width of the source electrode and/or the drain electrode of thebackup transistor, and wherein the length of the extending part of thesource electrode and/or the drain electrode of the backup transistor isless than the width of the first electrode line and/or the secondelectrode line.
 6. The driver circuit structure as claimed in claim 1,wherein the source electrodes of the transistors are connected inparallel, and/or the drain electrodes of the transistors are connectedin parallel.
 7. The driver circuit structure as claimed in claim 1 isapplied as a gate driver on array structure or a shift register of adisplay panel.
 8. The driver circuit structure as claimed in claim 1,wherein the transistors and the backup transistor have similarstructures.